In a network application, sometimes it is required to perform tracing according to an IP address used by a user for surfing the Internet. For example, a typical application scenario is that when illegal information appears on the Internet, a public security department needs to find a suspect who posts the illegal information, and can find user identity information of a suspect by tracing an IP address left by the suspect on the Internet.
An IPv4 address tracing method is already used on an existing IPv4 network. For example, during network access of a home broadband user by using the PPP over Ethernet (PPPoE) protocol, a broadband remote access server (BRAS) is responsible for transparently transmitting a user account and a password that are entered during a user authentication process to an authentication, authorization and accounting (AAA) server, and allocating, after receiving a result that is returned by the AAA server and indicates that authentication succeeds, an IPv4 address to a terminal used by the user. In addition, the BRAS may further report, in an accounting procedure, the foregoing user account and IPv4 address to the AAA server, so that the AAA server searches for corresponding user identity information according to the user account, and establishes a mapping relationship between the IPv4 address and the user identity information. Therefore, in subsequent tracing, identity information of the suspect may be found according to the IPv4 address left by the suspect, to implement tracing. It can be learned that, during the foregoing address tracing process, it is a user identifier (such as the foregoing user account) that associates the IPv4 address with the user identity information. Therefore, a key for the IPv4 address tracing is to find a user identifier corresponding to a to-be-traced target IPv4 address.
With large-scale deployment and commercial use of IPv6 in fixed networks and mobile networks, upgrading and reconstruction of IPv6-related systems are drawing increasing attention, where IPv6 address tracing, as an important security feature of IPv6, needs to be resolved. However, in existing IPv4 address tracing, a structure and an allocation manner of an IPv4 address are relatively simple, and reporting of an IPv4 address and a tracing method on the AAA side are both designed for an IPv4 address; while an allocation manner and an address structure of an IPv6 address are relatively complex and differ greatly from those of an IPv4 address. For example, an allocated IP address may be an IPv6 address, or an IPv6 prefix with a variable length. An existing IPv4 address tracing manner cannot implement tracing of an IPv6 address.